Information of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Assets:
Marketable Securities	$ 574,178		$ 567,302
Derivative assets	754		1,305
Total assets	574,932		568,607
Liabilities:
Junior subordinated notes, at fair value	12,740		11,911
CDO notes payable, at fair value	413,187		377,235
Derivative liabilities	95,974		113,331
Warrants and investor SARs	41,786		31,304
Total liabilities	563,687		533,781
Trading securities
Assets:
Marketable Securities	488,558		480,845
Trading securities | TruPs
Assets:
Marketable Securities	488,558		480,845
Trading securities | Other securities
Assets:
Marketable Securities	0		0
Security-related receivables
Assets:
Marketable Securities	84,990		86,455
Security-related receivables | Trups Receivables
Assets:
Marketable Securities	7,741		8,211
Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	32,932		33,046
Security-related receivables | CMBS receivables
Assets:
Marketable Securities	43,256	[1]	44,118	[2]
Security-related receivables | Other securities
Assets:
Marketable Securities	1,061		1,080
Available-for-sale Securities
Assets:
Marketable Securities	630		2
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative assets	0	[3]	0	[4]
Total assets	0	[3]	0	[4]
Liabilities:
Junior subordinated notes, at fair value	0	[3]	0	[4]
CDO notes payable, at fair value	0	[3]	0	[4]
Derivative liabilities	0	[3]	0	[4]
Warrants and investor SARs	0	[3]	0	[4]
Total liabilities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Trading securities | TruPs
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Trading securities | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | Trups Receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | CMBS receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Available-for-sale Securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2)
Assets:
Derivative assets	754	[3]	1,305	[4]
Total assets	78,633	[3]	79,551	[4]
Liabilities:
Junior subordinated notes, at fair value	0	[3]	0	[4]
CDO notes payable, at fair value	0	[3]	0	[4]
Derivative liabilities	34,611	[3]	45,926	[4]
Warrants and investor SARs	0	[3]	0	[4]
Total liabilities	34,611	[3]	45,926	[4]
Significant Other Observable Inputs (Level 2) | Trading securities | TruPs
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2) | Trading securities | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | Trups Receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	32,932	[3]	33,046	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | CMBS receivables
Assets:
Marketable Securities	43,256	[3]	44,118	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | Other securities
Assets:
Marketable Securities	1,061	[3]	1,080	[4]
Significant Other Observable Inputs (Level 2) | Available-for-sale Securities
Assets:
Marketable Securities	630	[3]	2	[4]
Significant Unobservable Inputs (Level 3)
Assets:
Derivative assets	0	[3]	0	[4]
Total assets	496,299	[3]	489,056	[4]
Liabilities:
Junior subordinated notes, at fair value	12,740	[3]	11,911	[4]
CDO notes payable, at fair value	413,187	[3]	377,235	[4]
Derivative liabilities	61,363	[3]	67,405	[4]
Warrants and investor SARs	41,786	[3]	31,304	[4]
Total liabilities	529,076	[3]	487,855	[4]
Significant Unobservable Inputs (Level 3) | Trading securities | TruPs
Assets:
Marketable Securities	488,558	[3]	480,845	[4]
Significant Unobservable Inputs (Level 3) | Trading securities | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | Trups Receivables
Assets:
Marketable Securities	7,741	[3]	8,211	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | CMBS receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Available-for-sale Securities
Assets:
Marketable Securities	$ 0	[3]	$ 0	[4]

[1] CMBS receivables include securities with a fair value totaling $10,134 that are rated between "AAA" and "A-" by Standard & Poor's, securities with a fair value totaling $25,181 that are rated "BBB+" and "B-" by Standard & Poor's, securities with a fair value totaling $6,860 that are rated "CCC" by Standard & Poor's and securities with a fair value totaling $1,081 that are rated "D" by Standard & Poor's.

[2] CMBS receivables include securities with a fair value totaling $8,228 that are rated between "AAA" and "A-" by Standard & Poor's, securities with a fair value totaling $26,594 that are rated between "BBB+" and "B-" by Standard & Poor's, securities with a fair value totaling $8,164 that are rated "CCC" by Standard & Poor's, and securities with a fair value totaling $1,132 that are rated "D" by Standard & Poor's.

[3] During the six-month period ended June 30, 2014, there were no transfers between Level 1 and Level 2, as well as, there were no transfers into and out of Level 3.

[4] During the year ended December 31, 2013, there were no transfers between Level 1 and Level 2, as well as, there were no transfers into and out of Level 3.